1. Field of the Invention
The present invention relates to an external lead bonding method and apparatus which are used to bond the external leads of solid-state devices punched out of a film carrier to lead frames or circuit boards.
2. Prior Art
The apparatus disclosed in the Japanese Patent Application Publication (Kokoku) No. 4-67782 is known as a conventional external lead bonding apparatus.
When the external leads of a solid-state device are aligned with and bonded to the leads of a lead frame in this apparatus, positional discrepancies may occur unless the solid-state device is fixed in place. In order to prevent such discrepancies, the apparatus includes a first bonding station and a second bonding station. At the first bonding station, bonding is performed on two opposite sides of the solid-state device which are not reached by the transporting arm to which the vacuum suction chucking head is attached. This bonding is performed with the solid-state device pressed against the lead frame by a vacuum suction chucking head which suction-chucks the solid-state device. At the second bonding station, the remaining two opposite sides of the solid-state device are subsequently bonded after the transporting arm has been withdrawn.
More specifically, a solid-state device which has been punched out of a film carrier by the punching of a punching apparatus is suction-chucked by the vacuum suction chucking head attached to the transporting arm and moved to a position above the first bonding station. Then, the solid-state device is lowered and pressed against the lead frame while still being held on the vacuum suction chucking head.
In this state, the leads on two opposite sides of the solid-state device are simultaneously bonded to the lead frame by the first bonding tool of a first bonding apparatus. Afterward, the first bonding tool is raised, and the vacuum suction chucking head is raised and moved to a position above the punching apparatus. The lead frame to which two opposite sides of the solid-state device have been bonded is then conveyed to the second bonding station, where the leads on the remaining two opposite sides of the solid-state device are bonded to the lead frame by the second bonding tool of a second bonding apparatus.
In this prior art, bonding is performed at two different bonding stations. Accordingly, two separate bonding apparatuses are required. As a result, it requires high equipment costs and a large installation space. Furthermore, since two bonding tools are used, attachment and level adjustment of the bonding tools must be performed at the respective bonding stations. Thus, it takes a relatively long time for accomplishing adjustment and maintenance.